Optical signal noise in optical transport networks can create problems. For example, such noise can limit the maximum span length and/or number of spans of the network. Such noise can also restrict the number of channels in a dense wavelength division multiplexing (DWDM) system and can limit the number of transparent optical network elements between 3R regeneration. Furthermore, optical signal noise requires tight component parameters.
Forward error correction (FEC) can counteract the effects of optical noise. Forward error correction includes Reed Solomon FEC (RSFEC), Enhanced FEC (EFEC) (such as EFEC provided by APPLIED MICRO CIRCUITS CORPORATION), and Ultra FEC (UFEC) (such as UFEC provided by CORTINA SYSTEMS).